U.S. Pat. No. 4,559,040 described an improvement to a miniature peristaltic pump in which a cartridge of the pump holds a rotor, a sleeve mounted on the rotor and a length of compressible tubing having opposite ends, wrapped around the sleeve. The cartridge is formed by two members, the "housing" and the "cover". The rotor is eccentrically formed to radially squeeze the resilient tubing. The tubing is in a single loop inside the circular pumping cartridge. The cyclic squeezing of the tubing by the rotor and the associated sleeve forces fluid from an inlet port to an outlet port of the pump.
Ideally, a disposable pump cartridge should be assembled and ready for insertion by connecting external inlet and outlet ports to tubing running from the source of medication to the patient. However, the structure of a closed continuous pump cartridge and the eccentricity of the rotor operate to pinch the resilient tube inside the chamber. Pinching of the tubing results in a permanent occlusion in the tubing. Further, pinching of the tubing also prevents gravity flushing of air bubbles from the system. If a chord segment is removed from the circumference of the pump cartridge for storage purposes, the resilient tubing is not pinched at a set position of the rotor high point during storage, and the tubing remains an open and resilient channel. The chord segment comprising a separate component associated with a motorized drive mechanism (motor frame) is combined with the cartridge immediately prior to use, to avoid an occlusion in the tubing during storage.
U.S. Pat. No. 4,559,040 describes such an improvement on a small peristaltic pump used in medical applications wherein a cartridge separate from the motor is preloaded with tubing and stored for future and rapid use. The cartridge described therein enables the tubing to be loaded with medicant by gravity flow while inserted in the head because the cap as not attached to the cartridge and the fluid passage through the cartridge is unoccluded.
The aforementioned U.S. patent describes a segmented cartridge for a peristaltic pump, wherein by removing a chord segment of the periphery of a pump chamber of the cartridge, an open area is created and the resilient tubing used by the peristaltic pump is not compressed during storage, thus avoiding occlusions and facilitating the flushing of air.
However, the implementation of the above-described cartridge into a pump motor frame resulted in a modification of the proposed design. The chord segment of the pump chamber removed from the cartridge was integrated into the pump motor frame, eliminating the need for a separate pump chamber segment. However, insertion of a cartridge lacking a portion of its pump chamber into a pump motor frame sometimes resulted in the pinching of tubing between the pump frame and the cartridge at the frame/cartridge interface, producing the occlusions sought to be avoided by the solution described in the above-noted patent.